And you thought Seattle's housing market couldn't get any tighter

The number of condo and house sales in the central Puget Sound region jumped 15 percent last month over the previous year, even as the number of residences for sale dropped precipitously.

The result: an even tighter housing market with home prices climbing at more than 9 percent, according to data the Northwest Multiple Listing Service (NWMLS) issued on Thursday.

In a balanced market, there is a four- to six-month supply of inventory. But in King County there was only 1.2 months of inventory last month, and several neighborhoods near Seattle's job centers had less than a month of supply.

It's not just King that has an acute shortage of homes for sale. NWMLS Director Dick Beeson of Tacoma said inventory in Pierce County is at a record low of 1.6 months.

"The stressed market is exhausting everyone in its path with no relief in sight," said Beeson, principal managing broker at RE/MAX Professionals.

As inventory has fallen, sales activity is at record high. During the first five months of the year, the number of pending sales in the four-county metro outpaced the previous record set in 2005, according to J. Lennox Scott, chairman and CEO of John L. Scott Inc.

Across King, Kitsap, Pierce and Snohomish counties, around 6,330 sales closed in May, or about 825 more than a year ago. Meanwhile, listings fell nearly 20 percent to around 10,250. That's more than 2,500 fewer homes available for buyers to choose from, causing prices to increase.

Combined, the median sale price for condos and houses in King County jumped 9 percent to $434,000 last month compared to May 2014. Snohomish County's median sale price hit $335,000 last month, up 9.8 percent. Kitsap's median price climbed 15.2 percent to $265,000, and prices in Pierce jumped almost 9.2 percent to a median of $250,000.

"We're still in desperate need of inventory," OB Jacobi, president of Windermere Real Estate said. "The irony is that there are plenty of people who want to sell, but won’t put their home on the market until they can buy something new," Jacobi said. "But they can’t buy something new until there are more homes on the market. It’s the proverbial chicken and egg situation for which I see no end in the near future.”